1. Technical Field
This invention relates to detergent bleach formulations containing a bleaching agent, that are suitable for washing fabrics and removing stains on fabrics. The bleaching agent can be hydrogen peroxide or a water-soluble peroxide adduct, e.g., one or more inorganic persalts which liberate hydrogen peroxide in aqueous solution such as alkali metal perborates, percarbonates, perphosphates, and persilicates.
Description of Related Art
Peroxide bleaching agents for use in laundering have been known for many years. Such agents are effective in removing stubborn stains from clothing such as tea, fruit and wine stains. However, the efficacy of peroxide bleaching agents drops off sharply below 60.degree. C. Consequently, bleach catalysts or heavy metal bleach activators have been employed to achieve satisfactory bleaching at the lower wash temperatures needed to avoid scalding of laundry workers and household consumers of laundry detergents. However, heavy metal catalysts, for example as described in U.S. Pat. No. 3,156,654, tend to promote the decomposition of hydrogen peroxide by reaction mechanisms which do not contribute to the desired bleaching effect, with consequent loss of bleaching performance. To control such loss of hydrogen peroxide, sequestrants for the heavy metals, such as ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DETPA) or their salts have been added to detergent bleach formulations. Unfortunately, sequestrants can also inhibit bleaching catalysis so that a balance is needed to maximize bleaching action while minimizing non-bleaching decomposition of the peroxide.
A related, but separate problem is the hydrolytic instability of heavy metal ions under normal (alkaline) wash conditions. Thus, in the absence of sequestering agents, heavy metal hydroxides will precipitate from solution and deposit themselves on the fabrics being laundered. Another problem is oxidative instability of heavy metal ions in the presence of certain non-peroxide oxidizing agents. For example, in the presence of hypochlorite, an oxidizing chlorine bleach which fastidious consumers may add to the wash water in the belief that it supplements the action of the peroxide bleaching agents in the detergent formulation, insoluble heavy metal oxides can form and become deposited on the fabrics. This can happen even in the presence of sequestering agents, which themselves are often susceptible to undesirable oxidation by hypochlorite.
Therefore, for a heavy metal to be useful as a bleach catalyst in a detergent bleach formulation, the heavy metal must not unduly promote peroxide decomposition by nonbleaching pathways and must be hydrolytically and oxidatively stable. The patent literature discusses the use of chelating agents to impart both hydrolytic and oxidative stability to the metal center. Thus, European Patent Application No. 84302774.9 describes the use of hydroxycarboxylic acids as "bleaching auxiliaries" to provide hydrolytic and oxidative stability to ferrous and ferric ions in solution. U.S. Pat. No. 4,478,733 discloses the use of Mn(II) as a peroxide bleach catalyst in detergent compositions containing perborate, aluminosilicate, and orthophosphate over the temperature range 20.degree.-60.degree. C. Likewise, U.S. Pat. No. 4,430,243 indicates that manganese (III) activates perborate bleaching in a detergent formulation. However, none of the prior art provides a heavy metal-based bleach catalyst that is entirely free of the foregoing drawbacks.
Accordingly, it is an object of the present invention to provide new, improved detergent bleach formulations.
Another object of the invention is to provide aqueous laundry wash media containing new improved detergent bleach formulations.
Another object of the invention is to provide new, improved bleaching agent compositions for use in detergent formulations.
Another object is to provide a new system for catalyzing the action of bleaching agent compositions.
Yet another object is to provide a method of producing a new system for catalyzing the action of bleaching agent compositions.
These and other objects of the invention as well as a further understanding of the features and advantages thereof, can be had from the following description and claims.